1. Field of the Invention
The present invention relates generally to a method for giving early indication of possible irregularities in the alignment of a engine timing apparatus. More particularly, the present invention relates to a method for giving early indication to an operator and service technician of an engine when a timing belt skips a tooth, a timing chain skips a link, or a timing gear skips a tooth.
2. Description of the Related Art
In belt, chain, or gear driven overhead camshaft engine designs, timing belt, chain, or gear slippage can occur. If such slippage does occur, misalignment between the camshaft and crankshaft will result. The cause of timing belt, chain, or gear slippage is commonly the result of low belt, chain, or gear tension. This slippage can also be attributed to debris entering the timing cover or wear on the timing apparatus. Timing belt, chain, or gear slippage may lead to such undesirable conditions as excessive emissions, poor vehicle performance, bent valves, an aperture being punched in the cylinder head, or piston damage.
Vehicles currently provide clearance so that the intake/exhaust valves and the pistons do not interfere with each other during engine operation. Such clearance is provided by placing cuts or indentations in the top of each piston. A large clearance via an indentation in the top of each piston may prevent the pistons from interfering with the intake/exhaust valves if the timing apparatus slips. The primary disadvantage to having a large indentation in the top of each piston is that raw fuel will collect and rest in the indentations. This collection of raw or partial burnt fuel, that is expelled in the engine exhaust, will affect emission ratings. Since high emissions may result from deep indentations in the top of the piston, a large clearance between the piston and intake/exhaust valves cannot be designed into all engines. As a result, if a timing belt, chain, or gear slips, valve and piston interference may occur. Moreover, misalignment between the camshaft and crankshaft caused by timing apparatus slippage may lower engine performance and thereby reduce fuel economy. Therefore, it is desirable in the art of vehicles to have an early detection device for possible timing belt, chain, or gear slippage.